Mad about Science: Swainson’s thrush

By Brenden Bobby
Reader Staff

June in Idaho means different things to different people; for some it’s a great time to drop the boat in the water, crack a cold beer on the lakeside and enjoy the quiet solitude of nature. Others take it as a great opportunity to trek deep into the woods and track down the myriad birds that haunt the shadowy copses covering our beautiful state.

Sitting idly in the shade for some time can reveal a cacophony of birdsong, ranging from the cheeseburger call of the black-capped chickadee to the punctuated du-du-du-du of migratory hummingbirds. Piercing through all calls of the forest is that of the Swainson’s thrush, a distinctive and ethereal call that’s very hard to describe as very little in the world shares a sound with this creature.

Avid hikers, cyclists and wanderers of Pine Street Woods would immediately recognize the call of the thrush, which seems to shift notes erratically while calling with an indescribable haunting resonance. The thrush is a bird you consistently hear when out in nature, but one you will almost never see.

The thrush is a migratory forest bird perfectly camouflaged for its preferred environment. Favoring alder forests, the thrush will migrate into our area during the late spring and early summer to live and breed. During the breeding season, a female will lay between three and five eggs in a nest and incubate them over the course of about two weeks. Both parents will work to feed the babies until they leave the nest, roughly another two weeks after hatching. The primary diet of the thrush is insects and other arthropods found on the forest floor. Despite commonly foraging the forest floor for food, spotting one in action can be an extremely rare occurrence. This is likely due to the camouflaged nature of the bird.

Swainson’s thrush is primarily a bark-brown color with buff speckling across its chest that fades into a cream white dotted by dark brown. In the shadow of the alders they prefer, the thrushes blend right in and audibly taunt you with their quirky call. One of the most distinctive features of the thrush is a cream colored ring around their dark black eyes.

Mating pairs of thrushes work in teams with the male singing to defend their claim against other pairs. The female will do all of the heavy lifting by constructing the nest herself. The females pack all sorts of materials into their nests, scavenging virtually anything they can transport including twigs, strips of bark, moss, grass and even mud to paste it together. The nest will often resemble a cup tucked away in a bush or the limbs of a tree. Female thrushes tend to favor locations ten feet from the ground or lower, though they have been observed to build nests as high as thirty feet off the ground.

Though the Swainson’s thrush’s conservation status is considered low concern, the changing climate and warming of the Northwest has presented some unique challenges to the species. They have shown a notable decline along the Pacific Coast. It’s hard to pinpoint a single reason as to why this may be the case, as it is likely a web of issues ranging from loss of habitat to human development and a decline in insect populations due to a rapidly altered climate.

The thrush has long legs in relation to its body with inverted knees that bend backward towards the tail. They’re roughly the size of a robin and could be easily mistaken for one at a glance, though robins in our area have bright red or orange underbellies while the thrush does not.

The thrush is a close relative of our state bird, the mountain bluebird. This is pretty shocking when you look at images of the birds side by side as they look nothing alike and are completely different colors.

The Swainson’s thrush has a long lifespan for a wild bird, capable of surviving up to 11 years, though doing so is rare. Most of these birds only survive for about two years due to predation, inclement weather, disease and other factors. These birds have many natural predators ranging from raptors to foxes, weasels and especially domesticated cats. An even larger variety of creatures will prey on thrush eggs and chicks, including crows, racoons, squirrels and snakes. The bird’s preferred nest height makes it easy for these predators to feed on them, should they find the birds to begin with.

Swainson’s thrushes aren’t usually attracted to feeders left out by humans. Generally shy and secretive birds, they aren’t as willing to compete with their more aggressive neighbors like woodpeckers. However, adding a water feature such as a fountain or a bird bath increases the chances of luring a thrush into your backyard, should you live reasonably near a copse of trees that may provide the thrush shelter. You’re more likely to see these towards the outskirts of town, while other members of the thrush family such as robins will be a little more adventurous in urban neighborhoods.

Are you interested in tracking down some birds for yourself? The library has a birding backpack available as a part of the Library of Things. Contained within this pack is a set of Vortex binoculars, Sibley Guide to western birds and a logbook you’re encouraged to write in. Please note, the logbook is the only item to be written in and the Sibley Guide should only be used for identification. There are two available at the Sandpoint library and one available in Clark Fork.

Additionally, stop by Pine Street Woods on Fridays, June 14; July 12; or Aug. 9 between 10 a.m. and 2 p.m. to borrow a pair of binoculars, collect samples and view your finds under a number of microscopes provided by the library during our Citizen Science series. 

I’ll be perched up at the parking lot with supplies perfect for families to explore the woods, find all sorts of interesting materials, and then observe and record them back at our mobile science center. This is a great time of year to explore your local ecosystem and maybe even find some rare birds while you’re at it.

In past years I’ve commonly spotted numerous black-capped chickadees, robins and I’ve heard the near-constant call of the Swainson’s thrush while sitting near the parking lot.

Stay curious, 7B.